Let's be clear on this; the original notice isn't really a 'penalty notice' - it's actually a dressed up Parking Charge Notice.
POPLA continue to contradict themselves at every turn.
The term 'owner' isn't convenient for them so, at a stroke, they change the word 'owner' to 'keeper' even though they know that the two terms have clearly defined meanings - there is no legal authority for the assessor to do this but he recognises the impossibility of the parking operators position if he doesn't wave his magic wand.
There's absolutely no legal requirement for the keeper to identify the vehicle owner.
Furthermore, one has to ask why anyone would ever appeal to POPLA in the first place if this really was a 'Penalty Notice' since POPLA would have no legal standing in getting such a statutory notice cancelled as they don't have the judicial powers required.
POPLA's involvement demonstrates that the notice is really a Parking Charge Notice which is issued in breach of the Code of Practice.
It will cost APCOA around £9,000 if they want to pursue this through the correct channels - any fine will go to the public purse.